Compressor and hydrogen station

ABSTRACT

A compression stage includes a cylinder, a piston, a first piston ring group, and a second piston ring group. The cylinder includes a first cooling channel through which a cooling fluid for absorbing heat generated between the cylinder and the first piston ring group flows, a second cooling channel through which a cooling fluid for absorbing heat generated between the cylinder and the second piston ring group flows, and an intermediate part disposed between the first cooling channel and the second cooling channel. A communication channel is connected to the intermediate part and a connection pipe, and guides a hydrogen gas leaking from a compression chamber through the first piston ring group to the intermediate part, to the outside of the cylinder.

FIELD OF THE INVENTION

The present invention relates to a compressor and a hydrogen station.

BACKGROUND ART

Conventionally, a reciprocating compressor configured to reciprocate a piston in a cylinder to compress gas in a compression chamber inside the cylinder has been known. In this compressor, a plurality of piston rings is installed on a piston outer peripheral surface such that the piston rings are aligned in an axial direction of the cylinder. This prevents the compressed gas obtained in the compression chamber from leaking through a gap between the piston outer peripheral surface and the cylinder inner peripheral surface.

For example, in a reciprocating compressor disclosed in Japanese Patent No. 5435245, a large number of piston rings divided into two piston ring groups are installed on a piston outer peripheral surface. Furthermore, the compressor disclosed in Japanese Patent No. 5435245 is provided with a gas introduction unit connected between the two piston ring groups to introduce gas. By this gas introduction unit, a gas having predetermined pressure is introduced into a gap between the piston outer peripheral surface and the cylinder inner peripheral surface.

In Japanese Patent No. 5435245, a compressed gas of predetermined pressure is introduced into a gap between a cylinder inner surface and a piston outer peripheral surface corresponding to between the two piston ring groups, thereby extending the life of the piston rings. It is considered that damage to the piston rings is cause by an increase in a load applied to the piston rings. That is, every time the gas that has passed through the first piston ring flows downstream and passes through each piston ring, the pressure of the gas decreases. Accordingly, the volume of the gas expands and the flow speed increases. This increases the load applied to the piston rings and causes damage. Therefore, by introducing the gas of predetermined pressure between the two piston ring groups, the flow speed of the gas flowing out to the piston ring group on the piston base end side is reduced, and as a result, the piston rings of the piston ring group on the piston base end side are protected.

However, in the compressor disclosed in Japanese Patent No. 5435245, the leaked gas generated in the compression chamber will pass through the piston ring group at a high temperature, which may accelerate wear of the piston rings.

SUMMARY OF THE INVENTION

An object of the present invention is to inhibit wear of piston rings in a piston provided with two piston ring groups.

A compressor according to one aspect of the present invention is a compressor for compressing a hydrogen gas, and includes: a plurality of compression stages; and a drive mechanism configured to drive the plurality of compression stages. At least one compression stage out of the plurality of compression stages includes: a cylinder; a piston inserted into the cylinder; a first piston ring group installed on the piston; and a second piston ring group disposed closer to the drive mechanism than the first piston ring group. The cylinder includes: a first cooling channel through which a cooling fluid for absorbing heat generated between the cylinder and the first piston ring group flows; a second cooling channel through which a cooling fluid for absorbing heat generated between the cylinder and the second piston ring group flows; and a through hole provided in an intermediate part between the first cooling channel and the second cooling channel, and penetrating an inner surface and an outer surface of the cylinder. The compressor further includes a communication channel communicating with a suction channel connected to the through hole and to the at least one compression stage, or a lower-pressure channel with lower pressure than the suction channel, the communication channel guiding the hydrogen gas leaking from a tip of the piston through the first piston ring group into the intermediate part, to outside of the cylinder.

A hydrogen station according to one aspect of the present invention includes: the compressor; an accumulator for storing the hydrogen gas discharged from the compressor; and a dispenser for receiving supply of the hydrogen gas from the accumulator.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram schematically showing a configuration of a hydrogen station to which a compressor according to a first embodiment is applied;

FIG. 2 is a diagram schematically showing the compressor according to the first embodiment;

FIG. 3 is a cross-sectional view schematically showing a partial configuration of the compressor shown in FIG. 2;

FIG. 4 is a cross-sectional view schematically showing a partial configuration of the compressor shown in FIG. 2;

FIG. 5 is a diagram schematically showing part of a compressor according to a second embodiment;

FIG. 6 is a diagram schematically showing part of a compressor according to a third embodiment;

FIG. 7 is a diagram schematically showing part of a compressor according to a fourth embodiment; and

FIG. 8 is a diagram schematically showing a compressor according to a fifth embodiment.

DESCRIPTION OF EMBODIMENTS

Embodiments for carrying out the present invention will be described in detail below with reference to the drawings. Directional indicators such as “up” and “down” are used in the description, but these directional indicators are for the purpose of only clarifying the description and should not be interpreted in a limited manner.

First Embodiment

As shown in FIG. 1, a compressor 1 is provided in a hydrogen station 100. The hydrogen station 100 includes the compressor 1 for compressing a hydrogen gas, an accumulator 2 for storing the high-pressure hydrogen gas compressed by the compressor 1, and a dispenser 3 for supplying the high-pressure hydrogen gas from the accumulator 2 to a demand destination such as a fuel cell vehicle 4.

As shown in FIG. 2, the compressor 1 includes a plurality of compression stages (first to fifth compression stages 11 to 15) and a drive mechanism 5 that drives the plurality of compression stages 11 to 15. Each of the five compression stages 11 to 15 sequentially compresses and delivers a hydrogen gas. Of the five compression stages 11 to 15, the first compression stage 11, the third compression stage 13, and the fifth compression stage 15 are coupled with one another to constitute a first block part 6. Of the five compression stages 11 to 15, the second compression stage 12 and the fourth compression stage 14 are coupled with each other to constitute a second block part 7 provided separately from the first block part 6.

In the first block part 6, the third compression stage 13 is placed on the first compression stage 11, and the fifth compression stage 15 is placed on the third compression stage 13. Meanwhile, in the second block part 7, the fourth compression stage 14 is placed on the second compression stage 12. The first block part 6 and the second block part 7 are placed on the drive mechanism 5. Rotation of a crankshaft (not shown) of the drive mechanism 5 causes compression of the hydrogen gas in each of the compression stages 11 to 15. In each of the first block part 6 and the second block part 7, a so-called tandem structure compressor is constructed in which a plurality of pistons is connected in series to one piston rod.

The compressor 1 includes a gas introduction pipe 9 a, a first connection pipe 9 b, a second connection pipe 9 c, a third connection pipe 9 d, a fourth connection pipe 9 e, and a gas discharge pipe 9 f. The gas introduction pipe 9 a is connected to a suction port of the first compression stage 11. The first connection pipe 9 b connects the first compression stage 11 to the second compression stage 12. The second connection pipe 9 c connects the second compression stage 12 to the third compression stage 13. The third connection pipe 9 d connects the third compression stage 13 to the fourth compression stage 14. The fourth connection pipe 9 e connects the fourth compression stage 14 to the fifth compression stage 15. The gas discharge pipe 9 f is connected to a discharge port of the fifth compression stage 15. The gas introduction pipe 9 a, the first connection pipe 9 b to the fourth connection pipe 9 e, and the gas discharge pipe 9 f form a channel for flowing a hydrogen gas.

FIG. 3 is a diagram showing the third compression stage 13 and the fifth compression stage 15 in a simplified manner. As shown in FIG. 3, the third compression stage 13 includes a third cylinder 23 and a third piston 33 inserted into the third cylinder 23. The fifth compression stage 15 includes a fifth cylinder 25 placed on the third cylinder 23 and a fifth piston 35 inserted in the fifth cylinder 25. The third compression stage 13 is a compression stage preceding to the fifth compression stage 15. The third cylinder 23 is a cylinder on a low pressure side of the fifth cylinder 25. The third piston 33 is a piston on a low pressure side of the fifth piston 35.

Inside the third cylinder 23, a third compression chamber 23S is formed by the third cylinder 23 and the third piston 33. Inside the fifth cylinder 25, a fifth compression chamber 25S is formed by the fifth cylinder 25 and the fifth piston 35. A diameter of the third piston 33 is larger than a diameter of the fifth piston 35. The third piston 33 and the fifth piston 35 are connected to each other by a connecting rod 37.

A plurality of piston rings is installed on the outer peripheral surface of the fifth piston 35. The plurality of piston rings constitutes a first piston ring group 41 and a second piston ring group 42. That is, the first piston ring group 41 and the second piston ring group 42 are disposed at a distance larger than the distance between adjacent piston rings. A plurality of piston rings is installed on the outer peripheral surface of the third piston 33. The plurality of piston rings constitutes a third piston ring group 43.

Although not shown, the first compression stage 11 includes a first cylinder and a first piston inserted into the first cylinder. The third cylinder 23 is placed on the first cylinder. The first piston and the third piston 33 are connected to each other by a connecting rod, and a piston rod is connected to the first piston. The piston rod converts rotational motion of the crankshaft of the drive mechanism 5 into reciprocating motion of the first piston via a crosshead. Furthermore, the second compression stage 12 and the fourth compression stage 14 have a configuration in which a piston is disposed inside a cylinder, and the fourth cylinder is placed on the second cylinder.

FIG. 4 is a cross-sectional view schematically showing the fifth compression stage 15. FIG. 4 illustrates the fifth compression stage in more detail than FIG. 3. The fifth cylinder 25 of the fifth compression stage 15 includes a cylinder body 51, a cylinder head 52, a suction side joint member 53, a discharge side joint member 54, an upper jacket member 55, and a lower jacket member 56.

The cylinder body 51 has a long shape in one direction (vertical direction in the illustrated example). A columnar space 51 a extending in the one direction is formed in the center thereof. The columnar space 51 a penetrates the cylinder body 51 in the vertical direction. An opening 51 b thereof is formed on the upper surface of the cylinder body 51.

The cylinder body 51 includes a body head 61, an upper tube part 62, an intermediate part 63, and a lower tube part 64. Note that in the cylinder body 51, these parts 61 to 64 are integrally formed. The body head 61 is located at the upper end of the cylinder body 51 and protrudes laterally (direction orthogonal to the one direction) from the upper tube part 62. On the upper surface of the body head 61, an upper surface recess 61 a, which has a circular shape when viewed from above and shares a center point with the opening 51 b and has an outer diameter larger than the outer diameter of the opening 51 b, is formed to be recessed downward.

A suction hole 61 b and a discharge hole 61 c are formed in the body head 61. The suction hole 61 b is a space communicating with the columnar space 51 a and extending in a direction orthogonal to the one direction, and is open on a side surface of the body head 61. The discharge hole 61 c is a space communicating with the columnar space 51 a and extending from the columnar space 51 a toward the opposite side of the suction hole 61 b. The discharge hole 61 c opens on a side surface of the body head 61 on a side surface opposite to the opening of the suction hole 61 b.

The upper tube part 62 has a tubular shape extending in the vertical direction, and is a portion having a constant outer diameter and disposed under the body head 61. The outer diameter of the upper tube part 62 is smaller than the outer diameter of the body head 61 and the intermediate part 63. The intermediate part 63 is disposed under the upper tube part 62. Therefore, the lower surface of the body head 61, the outer peripheral surface of the upper tube part 62, and the upper surface of the intermediate part 63 form an upper recess 51 c in the cylinder body 51. That is, the upper recess 51 c is formed in a ring shape to surround the outer peripheral surface of the upper tube part 62. The upper recess 51 c is covered with the upper jacket member 55.

The lower tube part 64 has a tubular shape extending in the vertical direction, and is a portion having a constant outer diameter and disposed under the intermediate part 63. The outer diameter of the lower tube part 64 is smaller than the outer diameter of the intermediate part 63. Note that the lower end of the cylinder body 51 located under the lower tube part 64 also has the same outer diameter as the intermediate part 63. Therefore, the lower surface of the intermediate part 63, the outer peripheral surface of the lower tube part 64, and the upper surface at the lower end of the cylinder body 51 form a lower recess 51 d in the cylinder body 51. That is, the lower recess 51 d is formed in a ring shape to surround the outer peripheral surface of the lower tube part 64. The lower recess 51 d is covered with the lower jacket member 56.

The cylinder head 52 includes a cylinder head body 52 a and a protrusion 52 b protruding downward from the lower surface of the cylinder head body 52 a. The cylinder head 52 is disposed on the upper surface of the body head 61 with the protrusion 52 b fitted to the upper surface recess 61 a of the cylinder body 51.

The suction side joint member 53 is used to hold a check valve (not shown) provided in the suction hole 61 b of the body head 61. The suction side joint member 53 is attached to the body head 61 to close the opening of the suction hole 61 b.

The discharge side joint member 54 is used to hold a check valve (not shown) provided in the discharge hole 61 c of the body head 61. The discharge side joint member 54 is attached to the body head 61 to close the opening of the discharge hole 61 c.

A through hole that allows the suction hole 61 b to communicate with the outside of the fifth cylinder 25 is formed in the suction side joint member 53. The fourth connection pipe 9 e is inserted into the through hole. The fourth connection pipe 9 e and the suction hole 61 b function as a suction channel of the fifth cylinder 25 that leads to the columnar space 51 a in the fifth cylinder 25 and causes the fifth compression chamber 25S, which will be described later, to suction a hydrogen gas.

A through hole that allows the discharge hole 61 c to communicate with the outside of the fifth cylinder 25 is formed in the discharge side joint member 54. The gas discharge pipe 9 f is inserted into the through hole. The gas discharge pipe 9 f and the discharge hole 61 c function as a discharge channel of the fifth cylinder 25 that leads to the columnar space 51 a in the fifth cylinder 25 and discharges a hydrogen gas from the fifth compression chamber 25S described later.

The upper jacket member 55 is disposed to cover the upper recess 51 c. With this configuration, a closed space is formed between the upper jacket member 55 and the outer peripheral surface of the upper tube part 62. This space functions as a first cooling channel 71 that cools the first piston ring group 41. The first cooling channel 71 has a size that covers the moving range of the first piston ring group 41 when the fifth piston 35 reciprocates. A cooling fluid for absorbing heat generated between the fifth cylinder 25 (inner surface of the cylinder body 51) and the first piston ring group 41 flows through the first cooling channel 71.

The lower jacket member 56 is disposed to cover the lower recess 51 d. With this configuration, a closed space is formed between the lower jacket member 56 and the outer peripheral surface of the lower tube part 64. This space functions as a second cooling channel 72 that cools the second piston ring group 42. The second cooling channel 72 has a size that covers the moving range of the second piston ring group 42 when the fifth piston 35 reciprocates. A cooling fluid for absorbing heat generated between the fifth cylinder 25 (inner surface of the cylinder body 51) and the second piston ring group 42 flows through the second cooling channel 72.

The upper jacket member 55 is provided with an introduction part 57 for introducing the cooling fluid into the first cooling channel 71. The lower jacket member 56 is provided with a discharge part 58 for discharging the cooling fluid from the second cooling channel 72. Note that the upper jacket member 55 may be provided with the discharge part 58, and the lower jacket member 56 b may be provided with the introduction part 57.

The fifth piston 35 has a long cylindrical shape in one direction (vertical direction in the illustrated example), and is vertically slidably disposed in the columnar space 51 a of the cylinder body 51. The tip surface (upper surface) of the fifth piston 35, the inner peripheral surface of the cylinder body 51, and the lower surface of the protrusion 52 b of the cylinder head 52 define the fifth compression chamber 25S. A micro gap C1 is formed between the inner peripheral surface of the cylinder body 51 of the fifth cylinder 25 and the outer peripheral surface of the fifth piston 35.

The intermediate part 63 is located between the first cooling channel 71 and the second cooling channel 72 in a direction in which the fifth piston 35 reciprocates. A through hole 63 a that allows the columnar space 51 a (micro gap C1) to communicate with the outside is formed in the intermediate part 63. One end of the through hole 63 a opens to the micro gap C1 and the other end opens to the outer peripheral surface of the intermediate part 63. A communication channel 81 is connected to the through hole 63 a, and the communication channel 81 is connected to the fourth connection pipe 9 e. That is, the leaked gas flowing out of the micro gap C1 is returned to the fourth connection pipe 9 e.

As a material for the communication channel 81, austenitic stainless steel having excellent corrosion resistance is preferably used. Examples of the material include Japanese Industrial Standards austenitic stainless steel pipes (JIS-G3459) SUS316LTP or SUS316TP, American Society of Mechanical Engineers austenitic stainless steel standard (ASME-Section 2 PART-A 1998 SA-479) XM-19, and the American Society of Mechanical Engineers austenitic stainless steel pipes standard (ASME-Section 2 PART-A 1998 SA-312) TPXM-19. Using the above-described materials for the communication channel 81 provides sufficient strength even in an environment where a high-pressure hydrogen gas flows, and hydrogen embrittlement is unlikely to occur.

The first cooling channel 71 and the second cooling channel 72 communicate with each other through a communication passage 63 b formed to penetrate the intermediate part 63. That is, a channel for flowing the cooling fluid is formed by the introduction part 57, the first cooling channel 71, the communication passage 63 b, the second cooling channel 72, and the discharge part 58. By allowing the first cooling channel 71 to communicate with the second cooling channel 72, the cooling structure in the fifth cylinder 25 can be simplified.

In the present embodiment, the communication passage 63 b is disposed at a position opposite to the through hole 63 a in the circumferential direction of the intermediate part 63, but may be disposed at another position as long as this position is different from the through hole 63 a in the circumferential direction of the intermediate part 63.

Note that the first cooling channel 71 and the second cooling channel 72 do not necessarily communicate with each other through the communication passage 63 b. In that case, the first cooling channel 71 and the second cooling channel 72 are each configured as an independent channel. The introduction part 57 for introducing the cooling fluid and the discharge part 58 for discharging the cooling fluid are provided in each of the first cooling channel 71 and the second cooling channel 72.

When the compressor 1 is driven, in each of the compression stages 11 to 15, the piston slides up and down inside the cylinder, whereby the compression chamber repeats expansion and compression. When the compression chamber expands, a hydrogen gas is introduced into the compression chamber. When the pressure in the compression chamber reaches predetermined pressure, the hydrogen gas is discharged from the compression chamber. As a result, the hydrogen gas introduced into the compressor 1 is sequentially compressed in the five compression stages 11 to 15 to become a high-pressure hydrogen gas, which is discharged from the compressor 1.

As shown in FIG. 4, part of the hydrogen gas compressed in the fifth compression chamber 25S flows out to the micro gap C1 corresponding to the first piston ring group 41 as the leaked gas in a high-temperature, high-pressure state. At this time, since the low-temperature cooling fluid circulates in the first cooling channel 71, the leaked gas is cooled while flowing through the micro gap C1, and the pressure decreases every time the leaked gas passes through the piston rings. As a result, it is possible to inhibit the expansion of the volume of the leaked gas and the increase in the flow speed, and to inhibit the wear of each piston ring of the first piston ring group 41 more than when the leaked gas is not cooled by the cooling fluid.

Part of the leaked gas flowing out of the micro gap C1 corresponding to the first piston ring group 41 is returned to the fourth connection pipe 9 e through the communication channel 81. The remaining hydrogen gas flows through the micro gap C1 corresponding to the second piston ring group 42. Since the communication channel 81 is provided, the amount of leaked gas flowing out to the second piston ring group 42 side is inhibited. This makes it possible to inhibit wear of each piston ring of the second piston ring group 42, and to reduce the amount of leaked gas leaking to the third compression stage 13 side through the micro gap C1 corresponding to the second piston ring group 42.

Since the low-temperature cooling fluid circulates in the second cooling channel 72, the leaked gas is cooled when flowing through the micro gap C1 corresponding to the second piston ring group 42. Therefore, it is possible to inhibit the wear of each piston ring of the second piston ring group 42.

The inner diameter of the communication channel 81 is preferably equal to or larger than 10% of the inner diameter of the fifth cylinder 25. The volume of the communication channel 81 is preferably larger than the volume of the micro gap C1 in the section corresponding to the first piston ring group 41 when the fifth piston 35 is stationary. By providing the communication channel 81 with predetermined volume, the communication channel 81 functions as a storage space into which the leaked gas can flow.

Second Embodiment

A compressor 1 of a second embodiment will be described with reference to FIG. 5. Note that the same components as in the first embodiment are denoted here with the same reference symbol, and detailed descriptions thereof will be omitted.

The second embodiment differs from the first embodiment in that a fifth compression stage 15 includes a distance piece 8. The distance piece 8 is adjacently disposed under a fifth cylinder 25. In the distance piece 8, a penetrating part 8 a for penetrating a connecting rod 37 connected to a fifth piston 35 is formed. In the distance piece 8, a space 8 b is formed to accommodate a leaked gas leaking through a micro gap C1 corresponding to a first piston ring group 41 and a second piston ring group 42. The distance piece 8 may be coupled with a third cylinder 23, or may be coupled with a drive mechanism 5.

When the compressor 1 is driven, part of the leaked gas leaking from a fifth compression chamber 25S through the micro gap C1 is returned to a fourth connection pipe 9 e through a communication channel 81. Therefore, the amount of leaked gas leaking from the fifth cylinder 25 into the distance piece 8 can be reduced.

Note that while the description of other configurations, actions, and effects will be omitted, the description of the first embodiment can be incorporated into the second embodiment.

Third Embodiment

As shown in FIG. 6, the third embodiment differs from the first embodiment in that a gas cooler 83 as a gas cooling unit is provided on a fourth connection pipe 9 e. Note that the same components as in the first embodiment are denoted here with the same reference symbol, and detailed descriptions thereof will be omitted.

A high-temperature, high-pressure hydrogen gas discharged from a fourth compression stage 14 is cooled by the gas cooler 83 and then introduced into a fifth compression stage 15. At this time, the gas cooler 83 is disposed downstream of a connection portion of a communication channel 81 in the fourth connection pipe 9 e. That is, the communication channel 81 is connected to a portion upstream of the gas cooler 83 in the fourth connection pipe 9 e. Therefore, the hydrogen gas returned from the communication channel 81 to the fourth connection pipe 9 e joins the hydrogen gas before being cooled by the gas cooler 83. Therefore, the high-temperature leaked gas flowing from the communication channel 81 to the fourth connection pipe 9 e can also be cooled by the gas cooler 83.

Note that while the description of other configurations, actions, and effects will be omitted, the description of the first embodiment can be incorporated into the third embodiment.

Fourth Embodiment

As shown in FIG. 7, the fourth embodiment differs from the first embodiment in that a check valve 84 is provided on a communication channel 81. Note that the same components as in the first embodiment are denoted here with the same reference symbol, and detailed descriptions thereof will be omitted.

While the check valve 84 allows a hydrogen gas to flow from within an intermediate part 63 (micro gap C1) into a fourth connection pipe 9 e, the check valve 84 blocks the flow of the hydrogen gas from the fourth connection pipe 9 e into the intermediate part 63 (micro gap C1).

When a compressor 1 is driven, pressure of the hydrogen gas in the fourth connection pipe 9 e may be higher than pressure of the hydrogen gas in the intermediate part 63 (inside micro gap C1). Even in this case, since the check valve 84 is provided on the communication channel 81, it is possible to prevent the inflow of the hydrogen gas from the fourth connection pipe 9 e into the intermediate part 63 (inside micro gap C1).

Note that while the description of other configurations, actions, and effects will be omitted, the description of the first embodiment can be incorporated into the fourth embodiment.

Fifth Embodiment

As shown in FIG. 8, the fifth embodiment differs from the first embodiment in that a pressure reducing valve 85 is provided on a communication channel 81, and that the communication channel 81 is connected to a lower-pressure channel with lower pressure than a fourth connection pipe 9 e (suction channel). Note that the same components as in the first embodiment are denoted here with the same reference symbol, and detailed descriptions thereof will be omitted.

For example, one end of the communication channel 81 is connected to a fifth cylinder 25 (intermediate part 63), and the other end is connected to a gas introduction pipe 9 a. Note that the other end of the communication channel 81 may be connected to a second connection pipe 9 c or a first connection pipe 9 b.

At this time, the pressure reducing valve 85 provided on the communication channel 81 reduces the pressure of the hydrogen gas on the intermediate part 63 side, which is a portion on a high pressure side, to predetermined pressure and flows the hydrogen gas to the gas introduction pipe 9 a, which is a portion on a low pressure side.

When a compressor 1 is driven, the pressure of the hydrogen gas in the intermediate part 63 (inside micro gap C1) may be significantly higher than the pressure of the hydrogen gas in the gas introduction pipe 9 a. However, since the pressure reducing valve 85 is provided, it is possible to prevent the hydrogen gas from excessively flowing from the intermediate part 63 into the gas introduction pipe 9 a.

Note that the communication channel 81 is not always connected to a fifth compression stage 15. For example, one end of the communication channel 81 may be connected to a fourth cylinder (intermediate part 63) of a fourth compression stage 14. In this case, the other end may be connected to the second connection pipe 9 c, the first connection pipe 9 b, or the gas introduction pipe 9 a. Furthermore, one end of the communication channel 81 may be connected to a third cylinder 23 (intermediate part 63) of a third compression stage 13. In this case, the other end may be connected to the first connection pipe 9 b or the gas introduction pipe 9 a.

Note that while the description of other configurations, actions, and effects will be omitted, the description of the first embodiment can be incorporated into the fifth embodiment.

It should be understood that the embodiments disclosed this time are in all respects illustrative and not restrictive. The scope of the present invention is indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and scope of the claims and equivalents are therefore intended to be embraced therein. Therefore, the following embodiments are also included in the scope of the present invention.

For example, the configuration in which the communication channel 81 is connected to the through hole 63 a formed in the intermediate part 63 of the cylinder body 51 may be applied to second to fourth compression stages 12 to 14.

In the first embodiment, the fifth compression stage 15 may be configured, for example, as a tandem structure with the preceding fourth compression stage.

The first compression stage 11, the third compression stage 13, and the fifth compression stage 15 do not have to be configured as a tandem structure. In this case, the first compression stage 11, the third compression stage 13, and the fifth compression stage 15 may be configured as separate bodies. Similarly, the second compression stage 12 and the fourth compression stage 14 do not have to be configured as a tandem structure. In this case, the second compression stage 12 and the fourth compression stage 14 may be configured as separate bodies.

Here, the above-described embodiments will be outlined.

(1) A compressor according to the embodiment is a compressor for compressing a hydrogen gas, and includes: a plurality of compression stages; and a drive mechanism configured to drive the plurality of compression stages. At least one compression stage out of the plurality of compression stages includes: a cylinder; a piston inserted into the cylinder; a first piston ring group installed on the piston; and a second piston ring group disposed closer to the drive mechanism than the first piston ring group. The cylinder includes: a first cooling channel through which a cooling fluid for absorbing heat generated between the cylinder and the first piston ring group flows; a second cooling channel through which a cooling fluid for absorbing heat generated between the cylinder and the second piston ring group flows; and a through hole provided in an intermediate part between the first cooling channel and the second cooling channel, and penetrating an inner surface and an outer surface of the cylinder. The compressor further includes a communication channel communicating with a suction channel connected to the through hole and to the at least one compression stage, or a lower-pressure channel with lower pressure than the suction channel, the communication channel guiding the hydrogen gas leaking from a tip of the piston through the first piston ring group into the intermediate part, to outside of the cylinder.

In the embodiment, the leaked gas leaking with expansion of volume and an increase in flow speed in the first piston ring group is cooled by the cooling fluid flowing through the first cooling channel. This makes it possible to inhibit the expansion of the volume and the increase in the flow speed of the leaked gas, and to inhibit the wear of each piston ring of the first piston ring group more than when the leaked gas is not cooled.

(2) The at least one compression stage and the preceding compression stage may have a tandem structure. In this case, the preceding compression stage may include: a low pressure side cylinder connected to the cylinder on a drive mechanism side; a low pressure side piston inserted into the low pressure side cylinder, connected to the piston, and having a diameter larger than a diameter of the piston; and a third piston ring group provided on the low pressure side piston.

In this aspect, the leaked gas in at least one compression stage can be released to the communication channel, and thus the amount of leaked gas leaking to the preceding compression stage can be reduced.

(3) The at least one compression stage may include a distance piece connected to the cylinder and for collecting the hydrogen gas that has passed through the first piston ring group and the second piston ring group.

In this aspect, the leaked gas in at least one compression stage can be released to the communication channel, and thus the amount of leaked gas leaking to the distance piece can be reduced.

(4) The suction channel may include a gas cooling unit for cooling the hydrogen gas flowing through the suction channel. In this case, the communication channel may be connected to a portion upstream of the gas cooling unit in the suction channel.

In this aspect, by connecting the communication channel to a portion upstream of the gas cooling unit, it is possible to prevent the gas cooled by the gas cooling unit from rising in temperature by the high-temperature leaked gas.

(5) The communication channel may be connected to the suction channel, and a check valve may be disposed on the communication channel.

The pressure of the hydrogen gas in the suction channel to which the communication channel is connected may be higher than the pressure of the hydrogen gas in the intermediate part. However, in this aspect, since the check valve is provided, the backflow of the hydrogen gas from the suction channel to the intermediate part can be prevented.

(6) The plurality of compression stages may include another preceding compression stage of the at least one compression stage. In this case, the low pressure channel may be a channel through which the hydrogen gas sucked into the another preceding compression stage flows. The communication channel may be connected to the low-pressure channel, and a pressure reducing valve may be disposed on the communication channel.

In this aspect, since the pressure reducing valve is provided, excessive outflow of the hydrogen gas from the communication channel to the low-pressure channel can be prevented.

(7) The intermediate part may include a communication passage that allows the first cooling channel to communicate with the second cooling channel at a different position in a circumferential direction from the through hole.

In this aspect, the first cooling channel and the second cooling channel communicate with each other, making it possible to simplify the cooling structure in the cylinder.

(8) An inner diameter of the communication channel may be 10% or more of an inner diameter of the cylinder, and volume of the communication channel may be larger than volume of a micro gap in a section corresponding to the first piston ring group out of volume of the micro gap between the piston and the cylinder.

It is necessary to increase the inner diameter of the communication channel in proportion to the inner diameter of the cylinder. Specifically, the inner diameter of the communication channel is preferably 10% or more of the inner diameter of the cylinder. The leaked gas is flowing into the micro gap, and it is necessary to make the volume of the communication channel larger than the volume of the micro gap. In this aspect, by providing the communication channel with predetermined volume, the communication channel functions as a storage space into which the leaked gas can flow.

(9) The hydrogen station includes: the compressor; an accumulator for storing the hydrogen gas discharged from the compressor; and a dispenser for receiving supply of the hydrogen from the accumulator.

As described above, the wear of the piston rings can be inhibited in the piston in which two piston ring groups are provided.

This application is based on Japanese Patent Application No. 2020-176172 filed on Oct. 20, 2020, the contents of which are hereby incorporated by reference.

Although the present invention has been fully described by way of example with reference to the accompanying drawings, it is to be understood that various changes and modifications will be apparent to those skilled in the art. Therefore, unless otherwise such changes and modifications depart from the scope of the present invention hereinafter defined, they should be construed as being included therein. 

1. A compressor for compressing a hydrogen gas, the compressor comprising: a plurality of compression stages; and a drive mechanism configured to drive the plurality of compression stages, wherein at least one compression stage out of the plurality of compression stages includes: a cylinder; a piston inserted into the cylinder; a first piston ring group provided on the piston; and a second piston ring group disposed closer to the drive mechanism than the first piston ring group, the cylinder includes: a first cooling channel through which a cooling fluid for absorbing heat generated between the cylinder and the first piston ring group flows; a second cooling channel through which a cooling fluid for absorbing heat generated between the cylinder and the second piston ring group flows; and a through hole provided in an intermediate part between the first cooling channel and the second cooling channel and penetrating an inner surface and an outer surface of the cylinder, the compressor further includes a communication channel communicating with a suction channel connected to the through hole and to the at least one compression stage, or a lower-pressure channel with lower pressure than the suction channel, the communication channel guiding the hydrogen gas leaking from a tip of the piston through the first piston ring group into the intermediate part to outside of the cylinder.
 2. The compressor according to claim 1, wherein the at least one compression stage and the preceding compression stage have a tandem structure, the preceding compression stage includes: a low pressure side cylinder connected to the cylinder on a drive mechanism side; a low pressure side piston inserted into the low pressure side cylinder, connected to the piston, and having a diameter larger than a diameter of the piston; and a third piston ring group provided on the low pressure side piston.
 3. The compressor according to claim 1, wherein the at least one compression stage includes a distance piece connected to the cylinder and for collecting the hydrogen gas that has passed through the first piston ring group and the second piston ring group.
 4. The compressor according to claim 1, wherein the suction channel includes a gas cooling unit for cooling the hydrogen gas flowing through the suction channel, and the communication channel is connected to a portion upstream of the gas cooling unit in the suction channel.
 5. The compressor according to claim 1, wherein the communication channel is connected to the suction channel, and a check valve is disposed on the communication channel.
 6. The compressor according to claim 1, wherein the plurality of compression stages includes another preceding compression stage of the at least one compression stage, the low-pressure channel is a channel through which the hydrogen gas sucked into the another preceding compression stage flows, the communication channel is connected to the low-pressure channel, and a pressure reducing valve is disposed on the communication channel.
 7. The compressor according to claim 1, wherein the intermediate part includes a communication passage that allows the first cooling channel to communicate with the second cooling channel at a different position in a circumferential direction from the through hole.
 8. The compressor according to claim 1, wherein an inner diameter of the communication channel is 10% or more of an inner diameter of the cylinder, and volume of the communication channel is larger than volume of a micro gap in a section corresponding to the first piston ring group out of volume of the micro gap between the piston and the cylinder.
 9. A hydrogen station comprising: the compressor according to claim 1; an accumulator for storing the hydrogen gas discharged from the compressor; and a dispenser for receiving supply of the hydrogen gas from the accumulator. 